Power circuit for electric machines



Aug. 14, 1928.

V. E. DUEMLER ET AL POWER CIRCUIT FOR ELECTRIC MACHINES Filed Jan. 19, 1925 Patented Aug. 14, 1928.

UNITED STATES PATENT OFFICE.

VIRGILE. DUE'MILER, OF MAPLEWOOD, AND GEORGE R. KOELN, OF ST. LOUIS, MIS- SOURI, ASSIGNORS. BY MESNE ASSIGNMENTS, T0 ELECTBOL, INC. OF MISSOURI, OF ST. LOUIS, MISSOURI, A CORPORATION OF MISSOURI.

rowan CIRCUIT non ELECTRIC MACHINES.

Application filed January This invention relates to a power circuit for an electric machine, with means for controlling the circuit. l

An object of the invention is to provide a circuit for an electrical machine havinga primary automatic switch for controlling the same, and a secondary switch operable automatically to open the circuit and .requiring manual setting before the circuit can be rendered operative. The advantages of the circuit will be apparent from the following detailed description taken in connection with the accompanying drawing, in which the circuit is diagrammatically shown.

The operating circuit for the electrical machine 1 comprises leads 2 and 3 connected with the power wires 4 and 5, a manual cutout switch 6 being provided for placing the leads of the operating circuit in circuit with' the power wires.

The circuit has a primary automatic switch 7 that may be of any type operated by temperature, pressure or the like. The switch 7 may be of any known commercial type of thermostatic or pressure construction. As illustrated diagrammatically in the drawing, the type is of the thermostatic construction in which one terminal of the switch is carried by a bimetallic member or plate which moves toward and away from a ermanently set contact point under the in uence of changes in temperature.

It is contemplated that the construction may be used for feeding fuel to a furnace or refrigerant to a refrigerator and that the switch 7 will be inserted in the element heated or cooled. When the motor is put in operation the means for changing the temperature is actuated and is followed by the o eration of the switch 7. A secondary switcii 8'is arranged for automatic operation in one direction to open the circuit, and reuiring manual operation to reset it before t e circuit may be operated.

The means for operating the switch 8 automatically comprises a-thermostatic element 9 associated with a shunt circuit 10 in which there is a resistance circuit 11. The continuation of the current through the shunt circuit 10 for a predetermined period of time deflects the free end of the thermo- 19, 1925. Serial No. 3,405.

static element 9 'until it contacts with a rocker arm 12 thereby opening the switch 8. After the switch 8 has once been opened 1t is necessary to reset it manually before the circuit to the electrical machine 1 can be completed.

When the switch 7 is open the circuit through the lead 2 is completed through the shunt circuit 10 until the switch 7 is closed. When, by reason of the fact that the resistance of the circuit through the switch 7 is less than through the shunt circuit, the current will flow through the switch 7 and away from the shunt circuit. If, for any reason, the primary switch fails to close, through failure of the automatic device for operating it, a continued passage of the current through the resistance circuit will open the switch 8, disabling the circuit until reset manually.

The shunt circuit also serves to cut down the are upon the opening and closing of the rent will be shunted away from the switch 7,

permitting completion of the opening thereof while the current passing thereto is reduced in voltage, thus preventin an arc at the contact points of the switch The circuit has application to many uses such, for instance, as to oil burners, refrigcrating devices and pressure generating devices, the switch 7 normall being under influence of the apparatus with which the circuit may be associated.

What we claim and desire to secure by Letters Patent is:

1. The combination with an electric machine, of a power circuit therefor, an automatic primary switch for saidcircuit, a

secondary switch movable manually to closed and automatically to open position, a shunt circuit connected across the automatic pri mary switch, said shunt circuit including a resistance element, and a thermostatic element in association with the resistance element for opening said secondary switch.

2. In combination with an electric machine, a power circuit therefor, an automatic switch in said power circuit, a shunt circuit connected across the automatic switch, a resistance element in said shunt circuit, a secondary switch in said power circuit, and means operable b the resistance element of said shunt circuit to open the secondary switch. v

3. In combination with an,,,e1ectric machine, a power circuit therefor, an automatic switch in said power circuit, a shunt circuit connected across the automatic switch, a resistance element in said shunt circuit, a secondary switch in said power circuit, means operable by the resistance element of said shunt circuit to open the secondary switch,

VIRGIL E. DUEMLER. GEORGE R. KOELN. 

